Various types and configurations of prosthetic heart valves, used to replace diseased natural human heart valves, are known in the prior art.
Prosthetic heart valves, at least those which include valve leaflets, can be generally categorized into one of two basic classes of replacement heart valves. The first class includes heart valves which have one or more relatively rigid leaflets formed of a stiff biocompatible material. The second class includes what will be referred to in this disclosure as bioprosthetic valves, which have flexible leaflets, typically made of a biological material. Among the known bioprosthetic valves, there are those which have a semi-rigid or relatively flexible frame or stent with (typically) three leaflets attached thereto, and those which have no stent. The stent in a stented replacement heart valve typically defines a substantially circular base of the valve body, around which an annular suture ring is disposed for suturing the valve to surrounding tissue, and further comprises commissure posts defining the juncture between adjacent leaflets.
Examples of bioprosthetic valves are described in U.S. Pat. No. 4,106,129 to Carpentier et al., entitled "Supported Bioprosthetic Heart Valve with Compliant Orifice Ring," and in U.S. Pat. No. 5,037,434 to Lane, entitled "Bioprosthetic Heart Valve with Elastic Commissures." The Carpentier et al. '129 patent describes a stent comprising a frame composed of a single flexible wire preformed to define a generally circular base which is interrupted at circumferentially-spaced points by three inverted U-shaped commissure posts which project generally normally with respect to the circular base. The Lane '434 patent describes a stent composed of a flexible metal ribbon similarly preformed to define three commissure posts which project generally normally with respect to a generally circular base. (This generally normally-projecting commissure support configuration exemplified by the Carpentier et al. '129 and Lane '434 patents is well-known in the art, and has alternatively been characterized in the prior art as comprising "axially-projecting" or "upwardly projecting" commissure supports.)
Both the Lane '434 and Carpentier et al. '129 patents describe a conventional configuration of three leaflets, wherein one leaflet is disposed between each pair of commissure posts.
The Hancock.RTM. Modified Orifice Aortic Bioprosthesis and the Hancock.RTM. M.O. II Bioprosthesis, manufactured by Medtronic, Inc., Minneapolis, Minn., are commercially-available examples of bioprosthetic valves. The Hancock.RTM. Modified Orifice Bioprosthesis, available since 1976, and the Hancock.RTM. M.O. II, available since 1978 are both available in various sizes, for example, 19-, 21-, 23-, and 25-mm, such that they may be implanted in patients having correspondingly varying sizes of aortic annuli.
To facilitate the implantation of heart valve prostheses, various types of specialized holders have been developed. Such holders are intended to enable the implanting surgeon to precisely position the heart valve and suture ring either within the heart passageway or adjacent/above the aortic root of the patient and to securely hold the valve assembly in place until suturing is complete and the sutures are tied Off.
Various prosthetic valve holders have been proposed in the prior art, including those discussed in U.S. Pat. No. 4,585,453 to Martin et al., entitled "Disposable Holder for Prosthetic Heart Valve," in U.S. Pat. No. 4,655,218 to Kulik et al., entitled "Prosthetic Valve Holder," in U.S. Pat. No. 4,679,556 to Lubock et al., entitled "Releasable Holder and Method of Use," in U.S. Pat. No. 4,683,883 to Martin, entitled "Two-Piece Heart Valve Holder/Rotator," in U.S. Pat. No. 4,801,015 to Lubock et al., entitled "Releasable Holder and Package Assembly for a Prosthetic Heart Valve," and in U.S. Pat. No. 4,865,600 to Carpentier et al., entitled "Mitral Valve Holder."
One problem which has been encountered during aortic valve replacement is that the laterally and upwardly projecting commissure posts can obstruct the surgeon's access to the valve base, making suturing of the suture ring to surrounding tissue and tying-off of the implanting sutures difficult. Such problems are particularly evident in patients having a relatively small aortic root.